The Journal of Neuroscience, September 15, 1998, 18(18):7381-7393
Sensory Processing in the Pallium of a Mormyrid Fish
James C.
Prechtl1,
Gerhard
von der Emde2,
Jakob
Wolfart1,
Saçit
Karamürsel3,
George N.
Akoev4,
Yuri N.
Andrianov4, and
Theodore H.
Bullock1
1 Neurobiology Unit, Scripps Institution of
Oceanography, University of California San Diego, La Jolla, California
92093, 2 Zoologisches Institut, Universität Bonn,
53115 Bonn, Germany, 3 Center for Electroneurophysiology,
Istanbul University School of Medicine, 34390 Istanbul, Turkey, and
4 Pavlov Institute of Physiology, Russian Academy of
Sciences, 199034 St. Petersburg, Russia
To investigate the functional organization of higher brain levels
in fish we test the hypothesis that the dorsal gray mantle of the
telencephalon of a mormyrid fish has discrete receptive areas for
several sensory modalities. Multiunit and compound field potentials
evoked by auditory, visual, electrosensory, and water displacement
stimuli in this weakly electric fish are recorded with multiple
semimicroelectrodes placed in many tracks and depths in or near
telencephalic area dorsalis pars medialis (Dm).
Most responsive loci are unimodal; some respond to two or more
modalities. Each modality dominates a circumscribed area, chiefly separate. Auditory and electrical responses cluster in the dorsal 500 µm of rostral and caudolateral Dm, respectively. Two auditory subdivisions underline specialization of this sense. Mechanoreception occupies a caudal area overlapping electroreception but centered 500 µm deeper. Visual responses scatter widely through ventral areas.
Auditory, electrosensory, and mechanosensory responses are dominated by
a negative wave within the first 50 msec, followed by 15-55 Hz
oscillations and a slow positive wave with multiunit spikes lasting
from 200 to 500 msec. Stimuli can induce shifts in coherence of certain
frequency bands between neighboring loci. Every electric organ
discharge command is followed within 3 msec by a large, mainly negative
but generally biphasic, widespread corollary discharge. At certain loci
large, slow ("
F") waves usually precede transient shifts in
electric organ discharge rate. Sensory-evoked potentials in this fish
pallium may be more segregated than in elasmobranchs and anurans and
have some surprising similarities to those in mammals.
Key words:
cerebral cortex; corollary discharge; induced rhythms; evoked potential; gamma band; lateral line; mormyrid
Copyright © 1998 Society for Neuroscience 0270-6474/98/18187381-13$05.00/0